Geometrically coated cathode-ray tube



March 10, 1953 w. H. NICKLESS ET AL 2,631,254

GEOMETRICALLY COATED CATHODE-RAY TUBE Filed Dec. 26, 1951 Patented Mar.10, 1953 UNITED STATE GEOMETRI ALLY COATED CATHODE-RAY TUBE William H.Nickless, Arlington, and Louis Grunfelder, Bergenfield, N. 3., assignorsto'Allied Electric Products, Inc Irvington, N. J., a cor-- poration ofNewJersey Application December 26, 1951, Serial No. 263,382

2 Claims. (01. 313-83) The invention herein disclosed relates to themanufacture of cathode ray tubes such as used in television receivers.

Particularly the invention is concerned with tubes of rectangular orother than circular shape.

These tubes are subject to cross burning of the picture screen, anaction which impairs the quality of the picture and reduces the usefullife of the tube.

Objects of the present invention are to eliminate and prevent thesecross burning effects and thus to maintain and prolong the pictureproducing quality and efficiency of the tube.

Other, related objects are to accomplish these results in a simple,practical way and without adding to actual cost of the tube.

Other desirable results and the novel features through which thepurposes of the invention are attained are set forth or will appear inthe course of the following specification.

The drawing accompanying and forming part of the specificationillustrates a present commercial embodiment of the invention. Theconstruction, however, may be modified and changed within the intent andscope of the invention as hereinafter defined and claimed.

Figs. 1 and 2 in the drawing are companion, broken sectional views of acathode ray tube incorporating the invention, Fig. 1 taken as on theplane of line ll of Fig. 2, and Fig. 2 taken as on the plane of line 2-2of Fig. 1;

Fig. 3 is a cross sectional view of the tube as taken on substantiallythe plane of line 3-3 of Fig. 1;

Fig. 4 is a perspective view looking inside the tube after removal ofthe front wall carrying the picture screen, the side wall portions ofthe tube indicated in section.

The tube shown is of the rectangular type, having a picture screen 5 atthe front, generally rectangular in shape and having a shallow groove 6in the side of the same, in back of the screen.

The inner surface of the tube is covered with a conductive coating 1,extending from the neck portion of the tube, 8, toward the screen.

This internal conductive coating serves to prevent cross reflectionswithin the tube and is used as a conductor, engaged by the contactsprings or snubbers on the gun which is inserted in the neck.

The usual practice has been to extend the internal coating all the wayto the groove 6 in the side of the tube, the bead 9 on the inside of thetube defining the location of this groove, being utilized as a markerlimiting the extent to which the coating is applied.

In the operation of tubes so constructed, the high potential on theinternal conductive coating creates lines of force extending from theedge of the coating across the face of the screen, these lines varyingin value according to the distance from the edge of the coating at oneside, across the screen to the edge of the coating at the opposite sideof the tube. The rectangular shape creating these lines of unequal forceestablishes a pattern on the screen, which eventually shows up as thecross burns on the screen.

Cross lines of unequal potential are avoided in the present invention bygiving the marginal edge of the internal conductive coating ageometrical contour such that radial lines extending from the center ofthe screen to the edge of the coating at opposite sides will all be ofequal length.

In the example illustrated this gives the marginal edge a scallopedoutline with deep concavities or recessions l0, Fig. 1, at the sides ofthe tube and similar recessions, l I, of lesser depth at the ends of thetube, Fig. 2, these curves joining and extending into points l2 at thecorners of the tube. These points are closest to the screen since thesecorners represent the greatest radial distance from the center of therectangular screen.

With the surface distance from the center of the screen to the edges ofthe coating constant for all radii, the potential across the screen fromone edge to the opposite edge of the coating will be substantiallyuniform and the electrical stress on the screen occasioned by thecoating, substantially equal at all points.

Cross burns and other objectionable results are thereby eliminated andat actually no greater cost in production. Less coating material isrequired but the coating is not reduced to the point where crossreflections will result.

While the coating contour shown, with scallops in the edge at the sidesand ends of the tube, is a proper form for rectangular tubes, it will berealized that conformation may vary in accordance with shape of thescreen, the main factor being that radial lines from the center of thescreen to edges of the coating should be substantially equal at allpoints.

What is claimed is:

1. A cathode ray tube having a noncircular picture screen, and aconductive coating on the inner surface of the tube extending from theneck portion of the tube toward the screen and terminating in anon-straight edge contour with the surface distance from the center ofthe screen to the edge of the coating substantially constant for all 3radii to present substantially equipotential radial lines extending inall directions through the center of the screen.

2. A cathode ray tube having a. generally rectangular picture screen anda neck portion in back of said picture screen, and a conductive coatingon the inner surface of the tube extending from said neck portion towardthe picture screen and terminating in a scalloped edge having curvedrecessions at the sides and ends of the tube, with those at the sides ofgreater depth. than those at the ends, and said curves at the sides andends joining in points closely approaching the back of the screen at thecorners of the generally rectangular formation and the surface distancefrom the center of the screen to the edge of the coating substantiallyconstant for all radii.

WILLIAM H. NICKLESS. LOUIS GRUNFELQER.

REFERENCES CITED The following references are of record in the file ofthis patent:

' UNITED STATES PATENTS Number 1 Name Date 2,233,786 Law Mar. 4, 19412,312,206 Calbick Feb. 23, 1943 52 138,668 Koch .1 Mar. 30, 19482,183,457 Feld et a1 Oct. 4, 1949 2,527,981 Bramley Oct; 31, 19502,533,334 Sunstein et a1 Dec. 12, 1950

